1. Field of the Invention
The present invention relates to a piping unit installed between an engine and a fuel tank to transport a fuel.
2. Description of the Related Art
Recently, as a control on exhaust emissions is tighten, a fuel injection system (injection system) of high fuel efficiency has been employed even in a compact vehicle with a small engine such as mini-vehicle, two-wheeled motor vehicle, three-wheeled motor vehicle, and all-terrain vehicle (ATV).
In this fuel injection system, a fuel is prepressurized, and the prepressurized fuel is injected only when a valve of an injector (fuel injection nozzle) is open. So, piping for transporting a fuel is required to have a pressure resistance of 0.25 to 0.35 MPa.
Therefore, when a rubber hose is used for piping, it is necessary to connect the rubber hose to a mating pipe by swaging a metal fitting onto an end portion of the rubber hose. In this case, there is a problem that this results in high production cost as well as troubles.
And, if the rubber hose is used, as an outer diameter of the rubber hose is large, there is a problem that an operator is considerably constrained from installing a piping unit through between components within a limited tight piping space.
On the other hand, a resin tube also has been conventionally used for transporting a fuel.
When such resin tube is adapted for piping, the resin tube is used in combination with a connector (quick connector) that permits simple and quick connection with a mating pipe.
In the resin tube, it is not necessary to swage a metal fitting onto an end portion of the resin tube for connection with the mating pipe, different from the rubber hose that is used for piping.
The connector of this type is disclosed, for example, in Patent Document 1 below.
FIGS. 11 and 12 show one instance of such connectors as disclosed.
In FIGS. 11 and 12, reference numeral 200 indicates a resin tube, reference numeral 202 indicates a mating pipe to be connected with the resin tube 200.
The mating pipe 202 is formed with an engaging projection (pipe-side engaging portion) 204 projecting annularly on an outer peripheral surface thereof.
Reference numeral 206 indicates a connector that has a connector body (here, entirely made of resin) 208, a retainer 210, a bush 214, and O-rings 212 as sealing member.
The connector body 208 includes a retainer holding portion 216 on one end of the connector body 208 along an axial direction (a proximal end or an axially outer end of the connector body 208), and a press-fit portion 218 on the other end thereof along the axial direction (a distal end or an axially inner end thereof) as connecting portion to the resin tube 200.
The press-fit portion 218 is a portion to be press-fitted or force-fitted within the resin tube 200 in an axial direction. The press-fit portion 218 is formed with annular ribs 220 at a plurality of axially spaced positions on an outer peripheral surface thereof. The annular rib 220 has a saw-edged cross-section and is provided with an acute angled peak.
The press-fit portion 218 is force-fitted within the resin tube 200 and thereby the connector body 208 is connected to such resin tube 200.
At that time, the annular ribs 220 formed on the outer peripheral surface of the press-fit portion 218 bite in an inner surface of an end portion of the resin tube 200 that is diametrically expanded and deformed by force-fitting of the press-fit portion 218, and thereby the resin tube 200 is retained and stopped for preventing withdrawal.
Meanwhile, the press-fit portion 218 is formed with an annular groove wherein an O-ring 222 is retained. The O-ring 222 provides an air-tight seal between the press-fit portion 218 and the resin tube 200.
The above retainer holding portion 216 is a portion for holding the retainer 210 while receiving the retainer 210 therein. The connector body 208 is connected to the mating pipe 202 via the retainer 210.
The retainer holding portion 216 is provided with a stop portion (body-side stop portion) 224 on a trailing end (proximal end or axially outer end) thereof for latching onto the retainer 210.
On the other hand, the retainer 210 is a resin member that is as a whole generally annular, and resiliently or flexibly deformable in a radial direction.
The retainer 210 is formed with an engaging recessed portion or engaging slit portion (retainer-side engaging portion) 225 and a latching recess (retainer-side latching portion) 226. The engaging projection 204 of the mating pipe 202 engages with the engaging recessed portion 225 from radially inward or inside the retainer 210. The latching recess 226 similarly fits to the stop portion 224 of the connector body 208 from radially inward or inside the retainer holing portion 216 to stop the retainer 210 in an axial direction.
The retainer 210 is held in the retainer holding portion 216 in an axially fixed state by latching the latching recess 226 onto the stop portion 224 of the retainer holding portion 216.
The retainer 210 further includes an inner peripheral surface thereof that defines a tapered inner peripheral cam surface 228, and an outer peripheral surface that defines a tapered outer peripheral cam surface 230.
When the mating pipe 202 is inserted inside the retainer 210 in an axial direction, the inner peripheral cam surface 228 abuts and guides the engaging projection 204 for further axial movement. Then the inner peripheral cam surface 228 resiliently diametrically expands the retainer 210 as a whole by the cam action as the engaging projection 204 moves and thereby allows passage of the engaging projection 204.
Then, as soon as the engaging projection 204 reaches a position of the engaging recessed portion 225, the retainer 210 as a whole returns to its original shape, the engaging projection 204 simultaneously is fitted or slipped in the engaging recessed portion 225 in fixed relation with one another in an axial direction.
On the other hand, when the retainer 210 is inserted in the retainer holding portion 216 of the connector body 208 in the axial direction, the outer peripheral cam surface 230 abuts the stop portion 224, thereby resiliently diametrically contracts the retainer 210 as a whole, and latches the latching recess 226 onto the stop portion 224 with diametrically contracting action of the retainer 210.
Meanwhile, the retainer 210 is provided with operation tabs 231 on trailing end portions (proximal end portions or axially outer ends) thereof. The retainer 210 also may be diametrically contracted by exerting a radially inward force to the operation tabs 231.
In the connector 206, the retainer 210 is first held in the retainer holding portion 216 of the connector body 208. Then, in this state, the mating pipe 202 is inserted inside the retainer 210 in the axial direction.
During that time, the retainer 210 is resiliently expanded in a diametrically expanding direction by the engaging projection 204 of the mating pipe 202. As soon as the engaging projection 204 reaches the engaging recessed portion 225, the retainer 210 diametrically contracts, and the engaging projection 204 engages in the engaging recessed portion 225.
On the other hand, the retainer 210 may be first attached to the mating pipe 202. Then, in this state, the mating pipe 202 with the retainer 210 thereon may be inserted in the connector body 208.
During that time, the retainer 210 diametrically contracts once, then, as soon as the latching recess 226 reaches a position of the stop portion 224, the retainer 210 diametrically enlarges to latch the latching recess 226 onto the stop portion 224.
The bush 214 and the O-rings 212 as sealing member are placed and retained, in a distal end of the connector body 208 relative to the retainer holding portion 216. When the mating pipe 202 is inserted within the connector body 208, the O-rings 212, or the O-rings 212 and the bush 214 contact air-tightly with an inserting end portion 232 of the mating pipe 202, namely an outer peripheral surface of a leading end (axially inner end) of the inserting end portion 232 relative to the engaging projection 204 (an outer peripheral surface of a leading end portion of the inserting end portion 232 extending from the engaging projection 204), and provide an air-tight seal between the mating pipe 202 and the connector body 208.
As shown in FIG. 11 (A), two O-rings 212 are used in the connector 206. However, as shown in FIG. 11 (B), as the case may be, single O-ring 212 may be used in the connector 206 for compact sizing of the connector 206.
As understood from the above, the resin tube 200 may be easily connected with the mating pipe 202 by use of such connector 206 with a simple action.
The conventional resin tube 200 here is, for example, about 6 mm in an inner diameter and about 8 mm in an outer diameter, and adapted in a piping system as shown in FIG. 13.
In this piping system, a fuel in a fuel tank 234 is transported (supplied) by a fuel pump 236 through a supply channel 238 under a certain pressure, and injected from an injector 240 to a cylinder 242 of an engine. And, a surplus fuel is returned through a return channel 244 to the fuel tank 234.
For assembling a piping system in a motor vehicle body, the resin tube 200 is first formed or molded in a bent or curved shape according to a predetermined piping layout and attached with connector 206 on each of or one of both ends of the resin tube 200. Then the resin tube 200 with connectors 206 thereon is delivered to an assembling site and assembled in the motor vehicle body on the assembling site.
However, the bent or curved resin tube 200 is obtained, for example, in the following steps. A straight tubular resin tube (a resin tube molded in a straight tubular shape) is fitted in a constraining mold to retain the resin tube in a bent or curved shape, and the resin tube as a whole or the constraining mold is put into an oven to be heated, for example, at a temperature of 150° C. to 160° C. for 20 to 30 minutes to be formed into a bent or curved shape, then, the constraining mold is taken out from the oven, cooled, and the resin tube is removed out of the mold (for example, as disclosed in Patent Document 2). However, many production steps are required or exist in this production method, resulting in increase of the production cost. And, here, the resin tubes 200 corresponding to the type of a motor vehicle, strictly speaking, corresponding to the type of the piping layout is required, and varied types of the resin tube should be produced accordingly. This is also a factor of the cost increase.
However, instead of a piping system (so-called a return fuel system) shown in FIG. 13 where a surplus fuel is returned to the fuel tank 234, another piping system, so-called returnless fuel system where a surplus fuel is not supplied but only a required quantity of the fuel, namely a quantity to be consumed is supplied from the fuel tank 234 to the engine has been increasingly applied recent years.
In the returnless fuel system, only the required quantity of the fuel is supplied. Therefore, if the resin tube 200 with the same diameter as in the piping system shown in FIG. 13 is used in the returnless fuel system, a fuel is likely accumulated. And, the fuel in accumulated state is evaporated in the piping under a certain atmosphere in the engine room, and resultantly, the engine revolutions are liable to be unstable.
In this case, for the resin tube 200, a small-diameter resin tube of an outer diameter up to 6 mm is preferably used in order not to cause accumulation of the fuel.
The resin tube with such small diameter has greater flexibility than a resin tube with large diameter. So, inventors of the present invention devised an assembling structure of a resin tube where the resin tube is not initially formed or molded in a bent or curved shape. The resin tube is formed or molded in a straight tubular shape and attached with a connector on each of or one of the both end portions thereof. Then, the resin tube equipped with the connectors or the connector thereon is delivered in an assembling site, and assembled for piping in a motor vehicle body by bending or curving the resin tube.
In this manner, a cost related to the resin tube may be lowered. And it becomes possible to use a common type of resin tube for various types of motor vehicles or various piping layouts in a versatile manner.
This assembling mode does not apply only to the resin tube with small diameter, but applies to resin tubes with relatively large diameter and excellent flexibility.
However, there is a problem that once a resin tube is broken (kinked) during assembly, the resin tube never returns to normal state and is never usable any more. So, in case where a resin tube is adapted for transporting a fuel, it is required that the resin tube is hard to be broken (buckled or kinked) when bent or curved.
By the way, such connector as described in Patent Document 3 may be used to be attached to an end portion of the resin tube 200. This connector 300 is, as shown in FIGS. 14 and 15, configured such that a relatively thin-walled retainer 302 is mounted on a retainer holding portion 304 in a direction perpendicular to an axis.
The connector 300 has a connector body (here, entirely made of resin) 306 in the form of a tubular shape as a whole, a retainer 302, O-rings 308 as sealing member and a bush 310 (refer to FIG. 14 (A)).
The connector body 306 includes a short cylindrical retainer holding portion 304 on one end of the connector body 306 along an axial direction and a connecting portion 312 on the other end thereof along the axial direction, for example, as connecting portion to the resin tube 200.
The retainer 302 in the form of a looped shape is configured by connecting a pair of engaging portions (retainer-side engaging portions, retainer-side latching portions) 314 integrally to V-shaped bodies 316 at one and the other ends of the engaging portions 314, respectively (refer to FIG. 14 (B). The retainer 302 is inserted in the retainer holding portion 304 via an opening 318 of the retainer holding portion 304 by narrowing a width of the retainer 302, and then the retainer 302 is returned to its original width (namely its original shape) in the retainer holding portion 304. The retainer 302 is located therein with its original shape.
When a mating pipe 202 (in the form of slightly different shape from the mating pipe 202 shown in FIG. 11) is inserted in the retainer 302, the engaging projection 204 of the mating pipe 202 abuts slant guide surfaces or slant guide cam surfaces 320 of the engaging portions 314. Then the engaging projection 204 pushes the slant guide cam surfaces 320 radially outwardly, and advances while widening the retainer 302. As soon as the engaging projection 204 passes through the engaging portions 314, the retainer 302 is slightly narrowed so that the engaging portions 314 engages with the engaging projection 204 in an axial direction (refer to FIG. 15). Here, the engaging portions 314 enter cutout portions (body-side stop portions) 322 of the retainer holding portions 304 and engage with the retainer holding portion 304 in the axial direction. In this manner, the mating pipe 202 and the retainer 302 or the connector body 306 are securely fixed in the axial direction. And, the mating pipe 202 may be pulled out of the connector 300 by pressing press portions 324 of the retainer 302 radially inwardly, and thereby widening a distance between the engaging portions 314. As shown in FIG. 16, in some case, enclosing portions 326 are formed in the opening 318 so as to rise radially outwardly in order not to allow the press portions 324 to protrude outwardly.
Or, a connector as shown in Patent Document 4 may be also used. This connector 400 is, as shown in FIGS. 17 and 18, configured such that a retainer 402 of a horse-shoe shape is mounted on a retainer holding portion 404 in a direction perpendicular to an axis. The connector 400 is provided further with a checker member 406 for verifying connection to the mating pipe 202.
The connector 400 has a connector body (here, entirely made of resin) 408 in the form of a cylindrical shape as a whole, a retainer 402, O-rings 410 as sealing member, a bush 412 and the checker member 406 (refer to FIGS. 17 and 18(B)).
The connector body 408 includes a short tubular retainer holding portion 404 on one end of the connector body 408 along an axial direction and a connecting portion 414 on the other end thereof along the axial direction, for example, as connecting portion to the resin tube 200.
The checker member 406 is shaped a box and includes a pair of resilient arms 416 and stop recesses 418 on end portions of the resilient arms 416. The checker member 406 is installed on an outer periphery of the retainer holding portion 404 in a direction perpendicular to an axis and is located in the retainer holding portion 404 so as to engage the stop recesses 418 with bottom surface portions 420, respectively.
The retainer 402 includes a pair of detecting lugs 422 and detecting detents 424 on end portions (free end portions) of the detecting lugs 422, and the detecting detents 424 protrude radially inwardly. The retainer 402 is mounted on an outer periphery of the retainer holding portion 404 in the direction perpendicular to the axis and is located in the retainer holding portion 404 so as to protrude the detecting detents 424 inside a passage of the engaging projection 204 of the mating pipe 202 (refer to FIG. 18 (A)).
When the mating pipe 202 is inserted in the connector body 408, the engaging projection 204 advances with pushing away slant guide surfaces or slant guide cam surface 425 and abuts the bush 412 (namely, the mating pipe 202 is correctly connected to the connector body 408), the detecting detents 424 of the retainer 402 are pushed and moved radially outwardly by the engaging projection 204, engagement of the detecting detents 424 and dents 430 of receiving slots 428 is cancelled, and thereby the retainer 402 is allowed to be further pushed in the direction perpendicular to the axis. When the retainer 402 is further pushed in the direction perpendicular to the axis, engaging portions (retainer-side engaging portions) 431 of the retainer 402 engage with the engaging projection 204 of the mating pipe 202, and simultaneously, the resilient arms 416 of the checker member 406 are moved by guide lugs 432 of the retainer 402, the stop recesses 418 of the resilient arms 416 are pushed radially outwardly, and thereby engagement of the stop recesses 418 and the bottom surface portions 420 is cancelled. In this manner, the mating pipe 202 and the connector body 408 are securely fixed together in the axial direction. In this securely fixed relation, the checker member 406 is allowed to separate from the connector body 408. That is, only when the mating pipe 202 is connected to the connector 400 correctly, the checker member 406 can be removed from the connector body 408. Meanwhile, the retainer 402 engages with restraining flanges 434, 436, 438 (body-side stop portions) of the connector body 404 at a rear end surface, middle recessed portions and a front end surface (retainer-side engaging portions) of the retainer 402 in an axial direction.    Patent Document 1 JP-A, 11-201355    Patent Document 2 JP-A, 6-190913    Patent Document 3 JP-B, 2641683    Patent Document 4 JP-A, 2004-251319